Polymerization utilizing a catalyst comprising a metal, a metal halide, and a metal oxide



United States Patent POLYMERIZATION UTILIZING A CATALYST COM- PRISING A METAL, A METAL HALIDE, AND A METAL OXIDE Omar O. Juveland, South Holland,' Herbert N. Friedlander, Homewood, and Edmund Field, Chicago, Ill., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana v No Drawing. Application May 29, 1958 Serial No. 738,655

/ V 13 Claims, c1. 26094.9)

This invention relates to novel polymerization catalysts and polymerization processes. The present invention provides processes suitable for the homoor hetero-polymerization of ethylene. By the processes of the present invention, ethylene can be polymerized to yield normally solid materials of controlled high molecular weight, especially highly crystalline, resinous materials, e.g. materials having densities (24/ 4 C.) in the range of about 0.95 to about 0.98.

Recently there have been disclosed a number of processes for polymerizing gaseous olefins to high molecular weight, normally solid polymers, employing as catalysts alkali metal hydrides or alkaline earth metal hydrides together with metal oxides of groups 5a and/or 6a of'the Mendeleeif Periodic Table, for example as described and claimed in U.S. Patent Nos. 2,726,231; 2,731,452; 2,773,053; and 2,791,575. While such processes are effective for the production of desirable polymeric materials from gaseous olefins over a broad temperature range, it has been found that such catalytic processes are most effective at elevated temperatures, preferably above 200 0, lower reaction temperatures resulting usually in a reduction in the rate of polymerization.

We have now found that substantially improved rates of polymerization of gaseous olefins to highly crystalline, resinous materials can be obtained with catalytic systems comprising alkali metal hydrides or alkaline earth metal hydrides together with metal oxides of group 5a and/or 6a and an effective amount of an aluminum halide. 'We have further found that ethylene can be readily polymerized in the presence of the novel catalysts of our invention at temperatures below the melting point of the polymeric product produced thus providing the art with a novel suspension polymerization technique for the preparation of high molecular weight ethylene polymers.

An object of our invention therefore, is to provide means for the preparation of novel olefin polymerization catalysts in situ from economical compounds of commerce. Another object is to provide the polymerization art with new cheap polymerization catalysts and methods for the preparation thereof. Yet another object is to provide novel suspension polymerization processes capable of polymerizing ethylene at low temperatures and pressures to highly crystalline polymers of high molecular weight. These. and other objects will become apparent from the following description of our invention.

In accordance with our invention, ethylene and the like can be polymerized readily under relatively mild operating conditions to produce commercially desirable solid polyme rs by contacting with catalysts prepared by mixing the following components in an inert liquid medium:

(a) A metal hydride selected from the group consisting of alkalimetal-hydrides and alkaline earth metal hydrides.

(b) An aluminum halide.

(c) A metal oxide selected from the group consisting 2 of oxides 'of transition metals of sub-groups 5a and 6a of the Mendeleeff Periodic Table.

The alkali metal hydrides are LiH, NaH, KH, RbH, and CsH of which the first three are now sufficiently economical to warrant commercial consideration. The alkaline earth-metal hydrides are BeH MgH CaH SrH and BaH The aluminum halide employed as a catalyst component can be aluminum trihalide of a single halogen element, eg AlCl ,'AlBr and the like or an aluminum trihalide containing diverse halogen atoms, e.g. aluminum chlorobromides and the like. The aluminum halide; can be used in the form of a double salt, a wide variety of which are known, including for example double salts of aluminum chloride and ammonium chloride, aluminum chloride and other metal chlorides suchas sodium chloride, potassium chloride, calcium chloride, and the like. We prefer to use AlCl because it is-readily available, cheap and effective. The inert-liquid medium used in our invention is usually a saturated or aromatic hydrocarbon which isla liquid under the polymerization conditions.

The metal oxide catalyst ingredients employed in the present invention are those of metals of group 5a and/or 6a (transition series members) of the periodic table, viz. V, Nb, Ta, Cr, Mo, W, U or mixtures thereof. vThe metal oxides are preferably extended upon suitable supports such as diflicultly reducible metal oxides including silica, activated alumina, titania, zirconia, clays and the like. The supported oxides are preferably calcined in air attemperatures between about 250 and about 700 C. before use to minimize the concentration of water and hydroxy groups in the catalysts and/or supports.

The proportion of group 5a or 6a metal oxide catalyst (including the catalyst support) with respect to the olefin charging stock, may vary from about 0.001 to about 20 Wt. percent, being not usually a critical feature of our process. The alkali metal hydride or alkaline earth metal hydride is supplied in an amount of at least one chemical equivalent per mole of aluminum halide employed in reaction mixture and preferably in an amount of at least one chemical equivalent per chemical equivalent of aluminum-halide. Larger proportions of alkali or alkaline earth metal hydride may be used, for example up to about 10 equivalents thereof per equivalent of aluminum halide or even more. 'The number of chemical equivalents of any component is the number of moles of said component times the positive valence of the metallic element in said component. In general the weight ratio of the sum of alkali metal hydride or alkalineearth metal hydride and aluminum halide to the metal oxide catalyst (including the catalyst support) is from about 0.01 to about 5.0 preferably from about 0.1 to 1.0.

The group 5a and/or 6a metal oxides are extended upon suitable supports and can be at least partiallyprereduced before use and preferably before contact with the other catalyst components by use of various reducing agents such as hydrogen, dehydrogenatable hydrocarbons, CO, H 8 or their equivalents. Mixed oxides or complex oxygen compounds of group 5a or 6a metals can also be employed in the present process. Thus, in addition suitable supports (having surface areas, for example, between about 1 and about 1500 square meters per gram), for example dirlicultly' reducible metal oxides such as alumina, magnesia, titania, zirconia, silica or their composites e.g. synthetic aluminosilicates, clays and the like. In some instances it'may be desired to employ a relatively low surface area support, of which a variety are known in the art, including tabular alumina, various fused silicates, silicon carbide, diatomaceous earths; various metals, preferably treated to produce a relatively thin surface coating of the corresponding metal oxide thereon, such as ironor steel containing a slight iron oxide coating, or aluminum carrying surface coating of alumina, e.g. as an anodized aluminum. We may also employ relatively high surface area, relatively non-porous supports or carriers for the group 5a and/or 6a metal oxide such as kaolin, zirconium oxide, iron oxide, pigments, carbon black or the like.

The relative proportion of support to the catalytic metal oxide is not critical and may be varied throughout a relatively Wide range starting upward from 1 part per 100. The usual catalytic metal oxide to support ratios are in therange of about 1:20'to about 1:1 or approximately 1:10 by weight. We may employ metal oxide catalysts composed of a supporting material containing about 1 to 80%, preferably about 5 to 35% or approximately 10% of vanadia or molybdena and other group 5a and/or 6a catalytic metal oxide supported thereon.

The group 5a or 6a metal oxide can be incorporated in the catalyst support in any known manner, for example, by impregnation, coprecipitation, co-gelling and/or absorption techniques which are well known in the catalyst art. It may be desired to confine the metal oxide almost completely to a surface film on the support, rather than to achieve deep impregnation of the support with metal oxide catalyst, in order to minimize mechanical disintegration of the catalyst by solid polymer.

In order to maximize the catalyst activity and reduce the requirements of alkali metal hydride or alkaline earth metal hydride co-catalyst, it is preferable to effect partial reduction of catalysts comprising group 5a metal pentoxides or hexavalent group 6a metal oxides before use in the polymerization process. The partial reduction and conditioning treatment of the solid metal oxide catalysts is preferably effected with hydrogen although other reducing agents such as carbon monoxide, mixtures of hydrogen and carbon monoxide (water gas, synthesis gas, etc.), sulfur dioxide, hydrogen sulfide, dehydrogenatable hydrocarbons, etc. may be employed. Hydrogen can be employed as a reducing agent at temperatures between about 350 C. and about 850 (3., although it is more'often employed at temperatures within the range of 450 C. to 650 C. The hydrogen partialpressure in the reduction or conditioning operation can be varied from subatmospheric pressures for example even 0.1 pound (absolute) to relatively high pressures up to 3000p.s.i.'g., or even more. The simplest reducing operation can be efiected with hydrogen at atmospheric pressure.

The proportion of group 5a and/or 6a metal oxide catalyst (including the support) based on the weight of the mono-olefinic charging stock, can range upwardly from about 0.001 weight percent to 20 weight percent or even more. In a polymerization operation carried out with a fixed bed of catalyst, the catalyst concentration relative to olefin can be very much higher. The efficiency of the supported group 5a or 6a metal oxide catalysts is extremely high in the presence of the alkali or alkaline earth metal hydride and aluminum halide co-catalysts, so that said metal oxide catalysts can be employed in very small proportions, based on the weight or charging stock, for example, between about 0.01 and about 10 weight percent, while maintaining high conversion efficiency.

The mixture of catalyst components is allowed to interact in the inert liquid medium 'at a temperature between about 20 C. and about 250 C. (preferably about 30 C. to about 175 C.) under an inert gas blanket or in the presence of the olefin to be polymerized. The promoting action of the alkali or alkaline earth metalhydride and aluminum halide co-catalysts may be enhanced if they are pre-reacted with the solid catalyst prior to admission of the olefin. Pre-reaction where desirable is carried out in the absence of olefin for from about 0.5 to about 4 hours, preferably 1 hour at temperatures between room temperature and C. The catalyst components can be allowed to interact in the presence of various stabilizing agents other than the olefin to be polymerized, e.g. other olefinic hydrocarbons, especially conjugated dienes such as butadiene, isoprene, styrene, indene and the like.

The catalyst concentration in the inert liquid medium is generally at least about 2 g. per 100 ml. and usually up to about 20 g. of even more per 100 ml.

The polymerization process of our invention can be effected over the temperature range of about 20 C. to about 250 C., but generally we use temperatures in the range of about 30 C. to about C., and preferably in the range of about 50 to about 150 C. In a preferred embodiment, the polymerization is effected at a temperature below the melting point of the polymer produced, that is below about 125 C., the process then being effectively a suspension polymerization process wherein the polymer precipitates from the reaction mixture as it is formed. By operating in this manner, crystalline polymeric products of extraordinary high molecular weight are readily obtained.

The polymerization pressure can be varied from less than one atmosphere e.g. /2 atmosphere to very high pressure of the order of 10,000 p.s.i.g., 15,000 p.s.i.g. or even more. The polymerization pressure can conveniently be set at about 1 to about 1000 p.s.i.g.

It is desirable to minimize or avoid the introduction of water, oxygen, carbon dioxide, acetylene or sulfur compounds into contact with the catalyst or co-catalyst. Any known means may be employed to purify the olefinic charging stocks of these materials prior to their introduction into the polymerization reactor.

The contact time or space velocity employed in the polymerization process will be selected with reference to the other process variables, catalysts, specific type of product desired and the extent of olefin conversion desired in any given run or pass over the catalyst. In general, this variable is readily adjustable to obtain the desired results. In operations in which the ethylene containing charging stock is caused to flow continuously into and out'of contact with the catalyst, suitable liquid hourly space velocities are usually between about 0.1 and about 10 volumes, preferably about 0.5 to 5 or about 2 volumes of olefin solution'in an inert liquid reaction medium per volume of solid catalyst. The amount of olefin in such solutions may be in the range of about 2 to 50% by weight, preferably about 2 to about 15 weight percent or, for example, about 5 to 10 weight percent.

The following specific examples are introduced as illustrations of our invention and should not be construed as an undue limitation thereof. The ethylene employed in the polymerization reactions was a commercial product containing oxygen in the range of about 15 to 50 ppm. The n-heptane employed as an inert solvent was a com mercial product thoroughly dried before use.

Example 1 A cc. rocker bomb was charged with 10 g. of a catalyst composition comprising 8 wt. percent molybdenum oxide on activated alumina (previously calcined for 20 hours at 570 C.), 100 cc. of dry n-heptane, 5.25 of calcium hydride and 1.66 g. of aluminum chloride. Ethylene was charged to the bomb and the contents of the bomb agitated and heated to a temperature of 127 C. Ethylene pressure at this temperaturewas maintained at 900-1000 p.s.i.g. for 22 hours. The reactor was then cooled and the Contents discharged and filtered. The solids so obtained were washed with methanolic HCl in a Waring Blendor, then filtered, washed with acetone and dried at 85 C. The solid polymer was extracted with xylene. It was found that 13.4 g. of solid polyethylene had been formed, having a melt viscosity of 1.8 poises (method of Dienes and Klemm, J. Appl. Phys. 17, 458 (1946)), and a density (24/4 C.) of 0.9691. In addition to the solid polymer, 1.2 g. of grease were isolated from the reaction product.

In the absence of aluminum chloride, otherwise employing the same charge-and conditions as above, only 1.06 g. of solid polymer having a melt viscosity of 3.7 10 and density (24/4 C.) of 0.9728 were formed.

7 Example 2 The procedure of Example was repeated employing the same charge and conditions, except that the supported metal oxide catalyst was reduced with hydrogen at 480 C. and atmospheric pressure for hours before use.

Solid polyethylene in an amount of 6.73 g. having a melt viscosity of 1.7)(10 poises and a density of 0.9638 was obtained.

Example 3 A 190 cc'. rocker bomb was charged with 10.0 g. of a calcined catalyst composition comprising 8 wt. percent molybdenum oxide supported on activated alumina, 100 cc.of dry n-heptane, 2.33 g. of calcium hydride and 0.74

g. of aluminum chloride. Polymerization of ethylene was effected at 900i000 p.s.i.g. and 150 C. for 22 hours. There was obtained 5.3 g. of solid polyethylene having a melt viscosity of 1.35 X10 poisesand density (24/4 C.) of 0.9650. None of the ethylene had been converted to gaseous or normally liquid products.

When the same charge was polymerized at a temperature of 171 C. for 4% hours, only 0.65 g. of solid polyethylene was obtained accompanied by 0.7 g. of grease.

Example 4 Following the procedure of Example 1, a charge comprising 10.0 g. of a calcined catalyst composition comprising 8 wt. percent molybdenum oxide on activated alumina, 100 cc. of n-heptane, 4.0 g. of sodium hydride, and 0.74 g. of aluminum chloride was pressured with ethylene and reacted at 900-1000 p.s.i.g. at a temperature of 127 C. for 22 hours. The solid polymer so obtained weighed 2.85 g. and had a melt viscosity of 1.7)(10' poises and a density (24/4 C.) of 0.9664.

Example 5 In this example, a 300 cc. rocker bomb was charged with 70 cc. of mineral spirits, 4.3 g. sodium hydride, 4.8g. aluminum chloride and 3.0 g. of a calcined catalyst composition comprising 8.7% molybdenum oxide on activated alumina which had been reduced with hydrogen at 500 C. and atmospheric pressure for 4 hours before A 300 cc. rocker bomb was charged with 70 cc. of dry n-heptane, 3.0 g. of a catalyst composition comprising 4.5 wt. percent chromium oxide on silica catalyst (previously ball-milled and calcined for 2 hours at 450 C.), 1.1 g. of lithium hydride and 3.6 g. aluminum cl1loride. Ethylene was pressured in to 350 p.s.i.g. at room temperature and the bomb contents then heated to 82 C. in /2 hour. Ethylene pressure was maintained at 300- 850 p.s.i.g. for 2.5 hours at 82 C. Recovery of the solid polymer so formed yielded 25 g. of polyethylene having an intrinsic viscosity of 5.76 dl./g. (determined at 130 C. on solutions of polymer in 100 cc. of decalin Containing 0.05 g. Ionol (2,6-di-tert-butyl-4-methyl- 6 phenol) as stabilizer) and density (24/4 C.) of 0.9779. In the absence of aluminum chloride, otherwise using the same charge and conditions, no solid polymer was obtained.

Example 7 Following the procedure of the ethylene was polymerized at 82 C. in the presence of 2.2 g. of calcium hydride, 4.8 g. aluminum chloride and 2.9 g. of a solid catalyst comprising 5.7 wt. percent vanadia on actuated silica (previously calcined at 450 C. in oxygen for 2 hours). Operation for 23 hours produced 31.4 g. of solid, high density polyethylene.

Although the novel catalysts and polymerization processes of the present invention have been generally described and specifically illustrated above, it will be appreciated that the invention is capable of very substantial extension therefrom.

Various monomers can be polymerized with ethylene and may be present in the reaction mixture in concentrations up to about 30 to 40 mole percent, based on ethylene.

' Vinyl alkene monomers which may be copolymerized with ethylene by the present polymerization process have the generic formula RCH=CH wherein R is an alkyl .radical. Specifically, suitable vinyl alkene feedstocks comprise propylene, isobutylene, .l-butene, l-pentene, 3- rnethyl-l-butene, l-hexene, t-butylethylene, tetrafluoroethylene. and mixtures of one or more of these alkenes or the like. s

The process of the present invention can also be applied to mixtures of ethylene with polyolefinic hydrocarbons, especially conjugated alkadienes e.g., 1,3-butadiene, isoprene, piperylene, 4-methyl-1,3-pentadiene or to nonconjugated alkadienes such as 1,5-hexadiene or the like.

Vinyl arenes are suitable feedstocks for use as comonomers with ethylene. Examples of vinyl arenes are styrene, nuclearly alkylated (especially methylated) styrenes, nuclearly halogenated styrenes and the like.

Polymerization is preferably performed in the presence of various reaction media which are liquid under the selected polymerization conditions of temperature and pressure. We prefer to. employ relatively insert liquid reaction media such as saturated hydrocarbons (alkanes and cycloalkanes), aromatic hydrocarbons, relatively unreactive alkenes or cycloalkenes, perfiuorocarbons, chloroaromatics or mixtures of suitable liquids, e.g. as described in United States Patent 2,692,257 of A. Zletz.

The polymeric products produced by the processes encompassed within the scope of our invention can be subjected to a variety of treatments designed to remove all or part of the catalytic materials therefrom.

Thus the hot polymeric solutions can be filtered for removal of solid catalyst, or the polymer can be extracted from the solid catalysts employed in the polymerization operation. The extracted polymer can be washed with water, methanol, alcoholic solutions of mineral acid. e.g. methanolic HCl or the like to remove traces of residual catalytic materials. Hot acetic acid extraction of ash from the polymers may also be practiced.

The polymers produced by the process of this invention can be subjected to such after-treatment as may be desired to fit them for particular uses or to impart desired properties. Thus, the polymers can be extruded, mechanically milled, filmed or cast-,- or converted to sponges or latices. Antioxidants, stabilizers, fillers, extenders, plasticizers, pigments, insecticides, fungicides etc. may be incorporated in the polyethylenes. The polyethylenes may be employed as coating materials, gas barriers, binders, etc. to even a wider extent than polyethylenes made by prior processes.

The polymers produced by the process of the present invention especially the polymers having high specific viscosities, can be blended with the lower molecular previous example weight polyethylenes to impart stiffness or flexibility or other desired properties thereto. The solid resinous products produced by the process of the present invention can likewise be blended in any desired proportions with bydrocarbon oils, waxes, such as parafiin r petrolatum waxes, with ester waxes, with high molecular weight polybutenes and with other organic materials. Small proportions between 0.1 and about 1 percent of the various polymers produced by the process of the present invention can be dissolved or dispersed in hydrocarbon lubricating oils to increase V.I. and to decrease oil consumption when the compounded oils are employed in motors. The polymerization products having molecular weights of 50,000 or more, provided by the present invention, can be employed in small proportions to increase the viscosity of fluid liquid hydrocarbon oils and as gelling agents for such oils.

The polymers produced by the present process can be subjected to chemical modifying treatments, such as halogenation. halogenation followed by dehalogenation, sulfohalogenation by treatment with sulfuryl chloride or mixtures of chlorine and sulfur dioxide, sulfonation and other reactions to which hydrocarbons may be subjected. The polymers of our invention can also be irradiated by high energy X-rays (about 0.5 to 2.5 m.e.v. or more) or by radioactive materials to effect cross-linking, increase in softening temperature and the like.

We claim:

1. A process for producing a normally solid polymer which comprises contacting ethylene with an inert liquid reaction medium containing a catalyst prepared by mixing (a) a member of. the class consisting of alkali metal hydrides and alkaline earth metal hydrides and (b) an aluminum halide selected from the group consisting of aluminum trichloride, aluminum tribromide and aluminum chlorobromides the amount of (a) being between 1 and about 30 chemical equivalents per mole of aluminum halide with (c) a supported catalyst comprising essentially a minor proportion of an oxide of a metal selected from the class consisting of group 5a and group 6a of the periodic table and mixtures thereof extended upon a major proportion of an inert solid supporting material comprising a difficultly reducible metal oxide the weight ratio of (a) plus (b) to (c) being in the range of from about 0.01 to about 5.0, said supported catalyst being present in an operative amount between about 0.001% and about by weight based on the weight of ethylene, effecting such contacting under superatrnos- 'pheric pressure at a suitable polymerization temperature between about C. and about 175 C. and recovering th'e equivalents ratio of (a) to (b) being between 1 and about 10 with (c) a supported catalyst comprising essentially a minor proportion of an oxide of a metal of group 5a of the periodic table extended upon'a major proportion of an inert solid supporting material comprising a difficultly reducible, metal oxide the weight ratio of .(a) plus (b) to (0) being in the range of from about 0.01 to about 5.0, said supported catalyst being present in an operative amount between about 0.001% and 20% by weight based on the weight of ethylene and recovering said normally solid polymer so produced.

4. A suspension polymerization process according to claim 3 wherein polymerization is effected at a temperature between about 50 C. and about C.

5. The process of claim 3 wherein said oxide is an oxide of vanadium.

6. In a polymerization process, the steps of contacting ethylene under polymerization conditions including a temperature between about 50 C. and about C. and a pressure between about 0 to 1000 p.s.i.g. with an inert liquid reaction medium containing a catalyst prepared by mixing (a) a member of the group consisting of alkali metal hydrides and alkaline earth metal hydrides (b) aluminum trichloride the equivalents ratio of (a) to (b) being between 1 and about 10 with (c) a supported catalyst comprising essentially a minor proportion of an oxide of a metal of group 6a of the periodic table extended upon a major proportion of an inert solid supporting material comprising a ditficultly reducible metal oxide the weight ratio of (a) plus (b) to (c) being in the range of from about 0.01 to about 5.0, said supported catalyst bein present in an operative amount between about 0.001% and 20% by weight based on the weight of ethy ene and recovering said normally solid polymer so produced.

7. A suspension polymerization process according to claim 6 wherein polymerization is effected at a temperature between about 50 C. and about 125 C.

8. The process of claim 6 wherein said oxide is an oxide of molybdenum supported upon alumina.

9. The process of claim 8 wherein said alkali metal hydride is sodium hydride.

10. A process for the homopolymerization of ethylene to a normally solid resinous polymer which comprises contacting ethylene in a liquid hydrocarbon reaction medium with a catalyst prepared by mixing calcium hydride, aluminum chloride and a supported catalyst comprising essentially a minor proportion of an oxide of molybdenum extended upon a major proportion of a difiicultly reducib e metal oxide, the equivalents ratio of calcium hydride to aluminum chloride being from about 1 to about 10, the weight ratio of calcium hydride and aluminum chloride to said supported catalyst being in the range of from about 0.01 to about 5.0, continuing said contacting at a temperature between about 50 C. and about 150 C. until said polymer has formed, and recovering a resinous polymer so produced.

11. A process for the homopolymerization of ethylene to a normally solid resinous polymer which comprises contacting ethylene in a liquid hydrocarbon reaction medium with a catalyst prepared by mixing lithium hydride, aluminum chloride and a supported catalyst comprising essentially a minor proportion of an oxide of chromium extended upon a major proportion of a difiicultly reducible metal oxide, the equivalents ratio of lithium hydride to aluminum chloride being between 1 and about 10, the weight ratio of lithium hydride and aluminum chloride to said supported catalyst being in the range of from about 0.01 -to about 5.0, continuing said contacting at a temperature between about 50 C. and about 150 C. until said polymer has formed, and recovering a resinous polymer so produced.

12. A novel composition consisting essentially of the reaction product secured by admixing (a) a member of the group consisting of alkali metal hydrides and alkaline earth metal hydrides (b) aluminum trichloride the amountof (a) being between 1 and about 10 chemical equivalent per mole of aluminum trichloride with (c) a supported catalyst comprising essentially a minor proportion of an oxide of a metal of group 5a of the periodic table extended upon a major proportion of an inert solid supporting materialcomprising a difiicultly reducible metal oxide the weight ratio of (a) plus (b) to being in the range of from about 0.01 to about 5.0.

13. A novel composition consisting essentially of the reaction product secured by admixing (a) a member of the group consisting of alkali metal hydrides and alkaline earth metal hydrides (b) aluminum trichloride the amount of (a) being between 1 and about 10 chemical equivalent per mole of aluminum trichloride with (c) a supported catalyst comprising essentially a minor proportion of an oxide of a metal of group 6a of the periodic table extended upon a major proportion of an inert solid supporting material comprising a difiicultly reducible metal oxide the weight ratio of (a) plus (b) to (0) being in the range of from about 0.01 to about 5.0.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR PRODUCING A NORMALLY SOLID POLYMER WHICH COMPRISES CONTACTING ETHYLENE WITH AN INERT LIQUID REACTION MEDIUM CONTAINING A CATALYST PREPARED BY MIXING (A) A MEMBER OF THE CLASS CONSISTING OF ALKALI METAL HYDRIDES AND ALKALINE EARTH METAL HYDRIDES AND (B) AN ALUMINUM HALIDE SELECTED FROM THE GROUP CONSISTING OF ALUMINUM TRICHLORIDE, ALUMINUM TRIBROMIDE AND ALUMINUM CHLOROBROMIDES THE AMOUNT OF (A) BEING BETWEEN 1 AND ABOUT 30 CHEMICAL EQUIVALENTS PER MOLE OF ALUMINUM HALIDE WITH (C) A SUPPORTED CATALYST COMPRISING ESSENTIALLY A MINOR PROPORTION OF AN OXIDE OF A METAL SELECTED FROM THE CLASS CONSISTING OF GROUP 5A AND GROUP 6A OF THE PERIODIC TABLE AND MIXTURES THEREOF EXTENDED UPON A MAJOR PROPORTION OF AN INERT SOLID SUPPORTING MATERIAL COMPRISING A DIFFICULTLY REDUCIBLE METAL OXIDE THE WEIGHT RATIO OF (A) PLUS (B) TO (C) BEING IN THE RANGE OF FROM ABOUT 0.01 TO ABOUT 5.0, SAID SUPPORTED CATALYST BEING PRESENT IN AN OPERATIVE AMOUNT BETWEEN ABOUT 0.001% AND ABOUT 20% BY WEIGHT BASED ON THE WEIGHT OF ETHYLENE, EFFECTING SUCH CONTACTING UNDER SUPERATMOSPHERIC PRESSURE AT A SUITABLE POLYMERIZATION TEMPERATURE BETWEEN ABOUT 30*C. AND ABOUT 175*C. AND RECOVERING SAID NORMALLY SOLID POLYMER SO PRODUCED. 